Method and devices for generating energy from photovoltaics and temperature differentials

ABSTRACT

A method for generating power is provided. The method including: providing a heat source with an output of radiation in a predetermined spectrum; generating a first portion of the power from the absorption of the radiation; and generating a second portion of the power from a temperature difference between a first element heated by the heat source and a second element at least partially thermally insulated from the first element.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of application Ser. No.10/720,507 filed on Nov. 24, 2003 now U.S. Pat. No. 7,326,850 whichclaims the benefit of earlier filed provisional application Ser. No.60/428,460, filed on Nov. 22, 2002, the contents of each of which areincorporated herein in their entirety by its reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to power generation, and moreparticularly, to methods and devices for generating energy fromphotovoltaics and temperature differentials.

2. Prior Art

Generators are well known in the art for generating electricity,particularly those known for use in back-up situations for residentialhomes, commercial buildings, and hospitals. Such devices generally havetwo-stroke engines that operate on gasoline. The output of such enginesis used to turn a generator, which produces electricity. The electricityis fed into the structure and/or supplied to an electrical grid. Suchtwo-stroke engines (and in some applications, 4-stroke engines) are usedin many other applications, such as lawn mowers and other outdoorequipment, small tractors, jet-skis and other recreational vehicles.Although, these engines have their advantages, they operate on ratherexpensive gasoline, significantly contribute to air pollution from theiremissions, have many moving parts and are therefore complicated, and areinherently inefficient, expensive, and noisy.

Furthermore, power is often required to be transmitted across a rotatingjoint; such joint can rotate in one, two, or three (spherical)directions. In the prior art, slip rings are used to provide anelectrical contact between the moving parts in the rotating joint. Suchslip rings are expensive to manufacture and maintain and are prone tofailure.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide methods and devicesthat overcome the disadvantages of the two and four stroke engines ofthe prior art by providing a cleaner burning, less expensive, lesscomplicated, more environmentally friendly, and more efficient methodand device for generating power.

It is another object of the present invention to provide an improvedalternative to the slip rings of the prior art that overcomes thedisadvantages of the slip rings

Accordingly, a method for generating power is provided. The methodcomprising: providing a heat source with an output of radiation in apredetermined spectrum; generating a first portion of the power from theabsorption of the radiation; and generating a second portion of thepower from a temperature difference between a first element heated bythe heat source and a second element at least partially thermallyinsulated from the first element.

The method can further comprise cooling the second element. The coolingcan generates a hot water byproduct.

The generating of the first portion of the power can comprise heating asecondary material to give off visible light. In which case the heatingof the secondary material can be such that it glows in a spectrum thatis most efficient for the generating of the first portion of the power.

Also provided is an apparatus for generating power. The apparatuscomprising: a heat source with an output of radiation in a predeterminedspectrum; a photovoltaic material for generating a first portion of thepower from the absorption of the radiation; and thermoelectric effectmeans for generating a second portion of the power from a temperaturedifference between a first element heated by the heat source and asecond element at least partially thermally insulated from the firstelement. The apparatus can further comprise cooling means for coolingthe second element. The cooling means can comprise a water jacketdisposed on the second element and a water supply for re-circulatingwater through the water jacket. The cooling means can also comprise afan for forcing an airflow across the second element.

The apparatus can further comprise a secondary material disposed betweenthe heat source and the photovoltaic material and which is heated by theheat source such that the secondary material gives off a visible lightthat is incident on the photovoltaic material. The secondary materialcan be heated such that it glows in a spectrum that is most efficientfor the photovoltaic material.

Still provided is a method for generating power across a rotatable jointwhere the rotatable joint has first and second rotatable elementsrotatably disposed relative to each other. The method comprising:providing a heat source with an output of radiation in a predeterminedspectrum in the first rotatable element; generating a first portion ofthe power from the absorption of the radiation from the first rotatableelement to the second rotatable element; and generating a second portionof the power from a temperature difference between a first elementheated by the heat source and disposed on the second rotatable elementand a second element disposed on the second rotatable element and atleast partially thermally insulated from the first element.

The method can further comprise cooling the second element. The coolingcan generate a hot air byproduct. One of the first and second elementscan have an interior and the method can further comprise heating theinterior at least partially with the hot air byproduct.

The generating of the first portion of the power can comprise heating asecondary material to give off visible light. In which case the methodcan further comprise heating the secondary material such that it glowsin a spectrum that is most efficient for the generating of the firstportion of the power.

Still provided is an apparatus for generating power across a rotatablejoint. The apparatus comprising: first and second rotatable elementsrotatably disposed relative to each other; a heat source disposed in thefirst rotatable element and having an output of radiation in apredetermined spectrum in the first rotatable element; a photovoltaicmeans in the second rotatable element for generating a first portion ofthe power from the absorption of the radiation from the first rotatableelement; and thermoelectric effect means for generating a second portionof the power from a temperature difference between a first elementheated by the heat source and disposed on the second rotatable elementand a second element disposed on the second rotatable element and atleast partially thermally insulated from the first element.

The apparatus can further comprise cooling means for cooling the secondelement. The cooling means can comprise a means for circulating airacross the second element to produce a hot air byproduct. Where one ofthe first and second elements has an interior, the interior can be atleast partially heated with the hot air byproduct.

The apparatus can further comprise a secondary material disposed betweenthe heat source and the photovoltaic means and which is heated by theheat source such that the secondary material gives off a visible lightthat is incident on the photovoltaic means. The secondary material canbe heated such that it glows in a spectrum that is most efficient forthe photovoltaic material.

Still provided is a back-up generator comprising: a heat source with anoutput of radiation in a predetermined spectrum; a photovoltaic materialfor generating a first portion of the power from the absorption of theradiation; and thermoelectric effect means for generating a secondportion of the power from a temperature difference between a firstelement heated by the heat source and a second element at leastpartially thermally insulated from the first element.

Still provided is a lawn mower comprising: a motor having a rotatableshaft; a cutting blade disposed on the shaft; a heat source with anoutput of radiation in a predetermined spectrum; a photovoltaic materialfor generating a first portion of the power from the absorption of theradiation; thermoelectric effect means for generating a second portionof the power from a temperature difference between a first elementheated by the heat source and a second element at least partiallythermally insulated from the first element; wherein at least a portionof the first and second portions of the power are supplied to the motorfor rotation of the shaft.

Still yet provided is a tank comprising: a tank body having a firstrotatable element; a turret having a second rotatable element rotatablydisposed on the first rotatable element; a heat source disposed in thefirst rotatable element and having an output of radiation in apredetermined spectrum in the first rotatable element; a photovoltaicmeans in the second rotatable element for generating a first portion ofthe power from the absorption of the radiation from the first rotatableelement; and thermoelectric effect means for generating a second portionof the power from a temperature difference between a first elementheated by the heat source and disposed on the second rotatable elementand a second element disposed on the second rotatable element and atleast partially thermally insulated from the first element.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the apparatus andmethods of the present invention will become better understood withregard to the following description, appended claims, and accompanyingdrawings where:

FIG. 1 illustrates a partial sectional view of a back-up generatoraccording to a preferred implementation of the present invention.

FIG. 2 illustrates a partial sectional view of a spherical joint inwhich power is delivered across the joint without the necessity of aslip joint according to a preferred implementation of the presentinvention.

FIG. 3 illustrates a sectional view of a lawn mower according to apreferred implementation of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Although the invention is particularly suited to the generation ofrelatively small amounts of power, those skilled in that art willappreciate that the devices disclosed herein may be scaled to producelarger amounts of power without any decrease in efficiency. Further,although a back-up generator, lawn mower, and spherical joint areillustrated and discussed herein, those skilled in the art willappreciate that the devices and methods of the present invention can beutilized wherever energy is required to power other elements, such as amotor, electronic components, or across any type of rotating orspherical joint.

Referring now to FIG. 1, there is shown an apparatus for producingelectrical power, the apparatus being generally referred to by referencenumeral 100. The apparatus has a heat source 102. The heat source can bea burner for burning a combustible gas, such as propane or natural gasfrom gas supply 104. A gas line 105 supplies gas to the heat source 102from the fuel supply 104. Generally, the fuel in the fuel supply 104 ispressurized, which facilitates supplying the same to the heat source. Avalve (not shown), which may be automatically controlled via aprocessor, can be supplied in the gas line 105 for selectivelyinterrupting the flow of gas from the fuel supply 104 to the heat source102. The heat source 102, such as a burner, operates in such a way thatis well known in the art to produce a hot flame. It is well known tothose skilled in the art how to achieve and maintain a hot flame from agas supply, therefore such details, such as valving and ignitors areomitted herein for the sake of brevity. However, such features (e.g.,ignitor, valving) may also be under the control of a processor).

The heat source 102 can also provide a source of radiation, preferablyvisible light, either directly or indirectly to power a photovoltaicdevice 106. In a direct configuration, the heat source 102 itselfproduces a visible light (e.g., from the flame of a burning gas), whichimpinges the photovoltaic device 106 to output an electrical power (P1).Photovoltaic materials and devices are well known in the art, as istheir operation. In general, photovoltaic materials convert visiblelight to electrical power. In an indirect configuration, the heat source102 heats a secondary material 108, such as ceramic, which is heated andglows, thus giving off visible light as a result of the heating. Thesecondary material 108 can be chosen such that it glows in a spectrumthat is most efficient for the photovoltaic device 106. The visiblelight from the secondary material 108 or directly from the heat source102 impinges the photovoltaic device 106 to output electrical power(P1). An air gap 107 can be provided between the heat source 102 and thesecondary material 108 or photovoltaic device 108.

In device 100, the electrical power output from the photovoltaic device106 is only a portion (P1) of the total electrical power output from thedevice 100. Preferably, electrical power (P2) is also output based on atemperature differential between hot and relatively cooler portions ofthe device 100. Preferably a thermoelectric cell (TEC) 110(alternatively referred to as a thermocouple cell) is utilized toproduce such power (P2). The use of TECs to produce electrical power iswell known in the art. Generally, TEC's generate electrical power from atemperature differential between a hot and cold side of the device.Although a single layer or stage of TEC is shown, those skilled in theart will appreciate that multiple layers or stages can be utilizedwithout departing from the scope of spirit of the present invention.TEC's having two or more stages are well known in the art.

One side (the hot side) 114 of the TEC 110 is disposed on a hot portionof the device, such as on the photovoltaic device 106 while the otherside 116 (the cold side) is disposed on a relatively cooler portion ofthe device. To increase the temperature differential between the hot andcold sides 114, 116 of the TEC 110, a cooler 112 (heat transfer device)can be provided on the cold side 116 of the TEC 110. The cooler 112 canbe an air-cooled device in which a fan (not shown) directs relativelycooler air across the cold side 116. Such fan can be powered by aportion of the output power (P1+P2) of the device. However, it ispreferred, particularly when using the device 100 as a back-upgenerator, that the cooler 112 have a water jacket 109 in which case theexcess heat from the device 100 is transferred to re-circulated waterand utilized as a source of hot or warm water. Although shown on asurface of the cooler 112, the water jacket 109 can also be disposed onthe surface of the cold side 116 of the TEC 110. The re-circulated watercan be pumped through the water jacket 109 by a pump (not shown), whichmay also be powered by a portion of the output power (P1+P2) or bynormal household or commercial water pressure. Therefore, in a powerfailure, the device 100 can supply both power and hot water to abuilding, including a residential home. Of course, the device 100 can besupplied with a covering enclosure 117 and may also have mounting means(not shown) for mounting the device to a floor, ground, or ground pad.The processor for controlling any valving, ignitor(s) and/or switches aswell as any internal wiring can be provided on or in the enclosure 117.

Thus, those skilled in the art will appreciate that a total power(P1+P2) output from the device 100 (and optionally hot water) can beefficiently produced from both the visible light output and temperatureoutput of the heat source 102. Those skilled in the art will alsoappreciate that the device 100 generates power with a cleaner burningfuel, in a less expensive manner, with a less complicated device havingvirtually no moving parts, which is more environmentally friendly (inboth air and noise pollutants), and more efficiently than the two andfour stroke engines of the prior art.

Referring now to FIG. 2, in which similar numbers denote similarfeatures to that of FIG. 1, there is shown a device for delivering poweracross a rotatable (in this case a spherical) joint, the device beingreferred to by reference numeral 200. Device 200 has first and secondmembers 202, 204 that have surfaces that move relative to each other.Although the device 200 has particular utility where the first andsecond members 202, 204 rotate relative to each, the invention is notrestricted to such movement, for instance, the first and second members202, 204 can also translate relative to each other. A simple bearing 206is shown as a schematic illustration only, and not to limit the rotationto a single direction, those skilled in the art will appreciate that thefirst and second members 202, 204 can rotate in two or three directions,such as in a spherical joint without limiting the scope or spirit of thepresent invention. The bearing 206 may also be disposed between surfaces208 and 210.

In device 200, the heat source 102, preferably from burning of acombustible gas from gas supply 104 is provided in a chamber 107 in thefirst member 202. As a result of the visible light generated eitherdirectly or indirectly from the heat source 102, a total power is outputat the second member 204 across the moving (e.g., rotatable) joint. Asdiscussed above, a first portion (P1) of the power is generated as aresult of the visible light impinging the photovoltaic device 106 andthe second portion (P2) is generated due to the TEC 110, which utilizesthe temperature differential between a hot side and cold side thereof.In non-generator backup applications it is preferred that the cold sideof the TEC 110 be air cooled with a fan (not shown) which suppliescooling air across the TEC 110. Those skilled in the art, willappreciate that the device 200 of the present invention generates anddelivers power across a moving joint with little expense, complexity,and likelihood for failure as compared to the slip rings of the priorart. The relative movement between the components of the joint can beany type known in the art, such as rotatable, spherical or linear.Although, the device 200 has utility in many applications, it hasparticular utility for a rotating turret in a tank, where the firstmember 202 is carried on the body of the tank and the second member 204is the movable turret. In such a configuration, the fuel supply 104 canbe separate from or the same as the fuel supply for the tank.Furthermore, any heat resulting from cooling of the cold side 116 of theTEC 110 can be used to heat the interior of the tank.

Referring now to FIG. 3, there is shown a device 300, which normallywould require a two or four stroke engine, having a power generationdevice of the present invention. Such a device 300 is illustrated, as alawn mower, however, those skilled in the art will appreciate thatnumerous portable devices would benefit from such power generationscheme. In the device 300, the power (P1 and P2) is provided to a motor302, which powers a blade 304 for cutting grass. In device 300, theblade 304 is housed in a housing 306 which rotatably supports wheels 308and a handle 310. The fuel supply 104, motor 102 and heat source 102 canbe housed in an enclosure 312. A fuel inlet 314 can be provided with acap 316 to refill the fuel supply 104 with fuel. Alternatively, theentire fuel supply 104 may be changed, such as a propane tank. Inportable devices, hot water is not usually necessary, therefore the coldside 116 of the TEC can be air-cooled. Air-cooling of the cold side 116of the TEC 110 can at least partly be provided by the blade 304 throughopenings 318 in the housing 306. Further openings 320 can be provided inthe enclosure to provide a cross-flow of air across the cold side 116 ofthe TEC 110.

The power generation schemes of the present invention can also be scaleddown to power small electronic devices. These small electronic devicescan include, but are not limited to handheld devices, such as cellularphones, laptop computers, and personal digital assistants (PDAs).

Although the apparatus of the present invention are shown with a singlestage of thermophotovoltaic units, those skilled in the art willappreciate that more than one such stage can be utilized. For example, afirst stage thermophotovoltaic unit can be disposed near the heat sourceand “tuned” to a first temperature. For purposes of this disclosure,“tuned,” means a temperature or temperature range at which thethermophotovoltaic unit, i.e., both the emitter and the photovoltaiccells, are most efficient. Since the amount of heat energy available tothe first thermophotovoltaic unit for conversion to electrical energy,i.e., the heat given off by the heat source, is much greater than theamount of heat that is actually converted to the electrical energy bythe first thermophotovoltaic unit since such units currently haveefficiencies of the order of 10-20%, the remaining heat (a differencebetween the heat of the heat source and the heat converted to electricalenergy in the first thermophotovoltaic unit) is dissipated throughconvection, conduction, radiation or otherwise. The remaining heat isthen used in connection with a second stage thermophotovoltaic unit thatis “tuned” to the second stage temperatures and the remaining heat ifadditional stages are to be employed. The stages can continue as long asthe temperatures are high enough for efficient power generation bythermophotovoltaic cells. Preferably, the heat from a stage isdissipated to a subsequent stage with forced convection of air or otherappropriate gaseous and/or fluid flow that can be generated by a fan ora pump and/or by conduction. The heat removed at one stage of thethermophotovoltaic cells is then used to heat the emitters of thefollowing thermophotovoltaic cells. The photovoltaic cells are alsopreferably insulated by relatively transparent materials that wouldefficiently transmit the radiated range of spectrum generated by theemitters in order to reduce the need for excessive cooling. Cooling ofthe photovoltaic cells is generally required since they operateefficiently at temperatures that are much below the temperatures thatthe emitter has to be heated to efficiently emit light within thedesired range of spectrum. In an embodiment of the present invention,one or more layers of thermoelectric cells are positioned behind thephotovoltaic cell elements to provide part or all the necessary cooling.The staging of the thermophotovoltaic materials units can continue untilthere is no useful temperature gradient and heat remaining, orpreferably, the thermophotovoltaic stages are used in combination withthermoelectric cells. In such a configuration, one or morethermoelectric cells are used as a last stage when the temperature andthe amount of heat remaining becomes low and within the operating rangefor the thermoelectric cells.

While there has been shown and described what is considered to bepreferred embodiments of the invention, it will, of course, beunderstood that various modifications and changes in form or detailcould readily be made without departing from the spirit of theinvention. It is therefore intended that the invention be not limited tothe exact forms described and illustrated, but should be constructed tocover all modifications that may fall within the scope of the appendedclaims.

1. An apparatus for generating power across a rotatable joint, theapparatus comprising: first and second rotatable elements rotatablydisposed relative to each other; a heat source disposed in the firstrotatable element and having an output of radiation in a predeterminedspectrum in the first rotatable element; a photovoltaic means in thesecond rotatable element for generating a first portion of the powerfrom the absorption of the radiation from the first rotatable element;and thermoelectric effect means for generating a second portion of thepower from a temperature difference between a first element heated bythe heat source and disposed on the second rotatable element and asecond element disposed on the second rotatable element and at leastpartially thermally insulated from the first element.
 2. The apparatusof claim 1, further comprising cooling means for cooling the secondelement.
 3. The apparatus of claim 2, wherein the cooling meanscomprises a means for circulating air across the second element toproduce a hot air byproduct.
 4. The apparatus of claim 3, wherein one ofthe first and second elements has an interior and the interior is atleast partially heated with the hot air byproduct.
 5. The apparatus ofclaim 1, further comprising a secondary material disposed between theheat source and the photovoltaic means and which is heated by the heatsource such that the secondary material gives off a visible light thatis incident on the photovoltaic means.
 6. The apparatus of claim 5,wherein the secondary material is heated such that it glows in aspectrum that is most efficient for the photovoltaic material.
 7. A tankcomprising: a tank body having a first rotatable element; a turrethaving a second rotatable element rotatably disposed on the firstrotatable element; a heat source disposed in the first rotatable elementand having an output of radiation in a predetermined spectrum in thefirst rotatable element; a photovoltaic means in the second rotatableelement for generating a first portion of the power from the absorptionof the radiation from the first rotatable element; and thermoelectriceffect means for generating a second portion of the power from atemperature difference between a first element heated by the heat sourceand disposed on the second rotatable element and a second elementdisposed on the second rotatable element and at least partiallythermally insulated from the first element.